Why "the Hum" gets louder at night ?
One of the mysteries surrounding "The Hum" is why does it seem to get louder or be more prevalent at night or in the wee hours of the morning This is a question I have had difficultly resolving until I stumbled upon this "Reccomended for you" Post One of the Comments describes a process call "Line Packing" that is employed with natural gas pipelines.
Without a doubt this explains why the Hum is louder at times and particularly louder at night.
What is Linepack ?
"Linepack" refers to the volume of gas that can be "stored" in a gas pipeline. Thinking back to basic chemistry, gas can be compressed (unlike liquids). Think of the classic example of compressing air in a bicycle pump. The air can be compressed into a smaller volume, or more air could also be squeezed into a fixed volume - for example a tyre.
The operational implications of line pack mean that the volume of gas injected into a pipeline (at the inlet), can bd greater than the volume of gas withdrawn from the pipeline (at the outlet). This frequently occurs due to the unpredictable nature of end-user operations and hence, their gas demand.
However, when gas is 'stored' in the pipeline by compressing it, the pressure exerted on all parts of the pipeline increases. The quantity of additional gas volume that can be stored in a pipeline depends on the pressure rating of the pipe, flanges, non return valves, compressors etc, as well as the ability for equipment upstream (before the inlet) and downstream (past the outlet) to respond to a sudden surge in pressure if inlet or outlet valves failure. This event is called a high-pressure/low-pressure breakthrough. When the pipeline pressure is high, it becomes increasingly difficult to inject additional gas into it. Compressors are used to increase the injection pressure of the gas.
The Hum is also prevalant whereever natural gas is being produced.
Not long after I started to look for the explanation for the World Hum someone told me about a Website and Database that contains accounts of "The Hum"
After my examination of the World Hum Site on a number of occasions I began to notice a corellation between reports of The Hum and a map of Countries that produce natural gas. Above is an illustraion of Australia's Pipelines and natural gas production facilities. As you can see there is a concentration of Hum reports in the areas where there is activity.
The image on the right is a map of Hum reports from the World Hum database The image on the left is a Map of natural gas Compressors in the US. Keep in mind that Infrasound and low Frequency noise generated by pipeline compressors can travel along the pipeline and through the air for great distances due the the length of the sound waves.
Prince Edward Island, which has no Gas Pipelines or processing facilities has zero accounts of the The Hum in the Database
Provincial and Territorial Energy Profiles – Prince Edward Island
Cavendish Farms is the biggest user of NG in the Province but it is trucked in.
Cavendish Farms now fuelled by natural gas - The Guardian - Updated: Sep 30, 2017 at 2:41 a.m.
The Evidence Page 1 - The Evidence Page 2